2002 Venture and Acceleration Problem?

I'm not sure how to describe it but my Venture will accelerate from 0 to 60 normally. However, from 60 on it is almost like the acceleration is on the slow side and eventually makes it. I don't hear or feel anything weird except it feels like the van doesn't have enough power when I accelerate and pick up speed. what can this be?
thanks

have you tried putting a new fuel filter on? mine starting loosing power and it ended up being the fuelpump which was $320.00 and still made in mexico